The original recording was a fast, Hammond organ-driven blues rock track released as a single by the Spencer Davis Group in early 1967, reaching number nine in the UK Singles Chart and number 10 in the U.S. (the US edition was slightly edited) Billboard Hot 100. It was the last hit single by the band before the brothers Steve and Muff Winwood left to pursue their own separate careers.

"I'm a Man" was included on the band's summer 1967 album, I'm a Man, as well as being featured on the 2005 Spencer Davis Group DVD Gimme Some Lovin' Live 1966. Although the recording is said to be late 1966, this date is in fact controversial. In an article and an interview on the "Living Archives" (Elävä arkisto) website of YLE, the Finnish Broadcasting Corporation, the producer of the original live recording, Mr. Tapani Karhu, clearly states that the date of the show was 19 March 1967.

Chicago Transit Authority (now known as Chicago) recorded a cover version of "I'm a Man" for their 1969 debut album, The Chicago Transit Authority. When the band's popularity surged after their second album, "I'm a Man" was released as the B-side to a re-release of "Questions 67 and 68". Radio stations ended up playing both sides, and "I'm a Man" reached #49 on the U.S. Billboard Hot 100 chart in 1971. The song reached #13 in Ireland.

...
Wikipedia